Internet Corporation for Assigned Names and Numbers
The Internet Corporation for Assigned Names and Numbers (ICANN) develops policies and does top-level management of various administrative machinery necessary to Internet operations. It is a QUANGO, or quasi-nongovernmental organization created by a Memorandum of Understanding from the U.S. Department of Commerce to an international group of "stakeholders". Key among these was the assignment of various identifiers that technically had to be unique on an Internet-wide basis (see locality of networks), such as Internet Protocol version 4 (IPv4) and now Internet Protocol version 6 (IPv6) addresses, names in the Domain Name Service, and other highly specialized identifiers such as autonomous system numbers, as well as identifiers specific to protocol (computer) families.
The Internet and its research predecessors, such as the ARPANET, were originally funded by part of the United States Department of Defense. As the Internet became more of a public and self-supporting resource, the U.S. government began to withdraw from supporting and operating these functions. ICANN was established as a replacement for the U.S. government in these roles, becoming more international, and including not just government, but commercial, academic, local government, user groups, and other concerns with legitimate interest in Internet policy.
ICANN does not have responsibility for day-to-day operations of the Internet. An analogy to its role might be with the international standards bodies that assign country codes for telephone numbers, with the national structure of a telephone number being a matter to be decided by national authorities.
Addresses and autonomous system numbers
The most basic function of ICANN is the Internet Assigned Numbers Authority (IANA), which manages suballocations from the IPv4 and IPv6 address spaces. IANA manages very large blocks, and delegates their detailed administration to regional address registries (RIR) that are on a roughly continental level. The RIRs also administer autonomous system numbers, another operationally significant resource that must be unique in the Internet.
Internet Assigned Numbers Authority
Address and internal identifier assignment is a relatively technical and noncontroversial area. There has been a conscious attempt to avoid the economic speculation and business-driven ploys common in DNS, as the numbers here are a finite resource, technical in nature, and essential to the proper operation of the entire Internet.
While the identifiers actually used to send packets through the Internet are a major administrative function, there are other identifiers, far less frequently changed, that must, for technical reasons, be unique. For example, the Transmission Control Protocol has a set of port numbers that identify certain standard values that will access a particular service on a computer. Port number 80 is assigned to the basic World Wide Web protocol, Hypertext Transfer Protocol, while port 25 goes to the Simple Mail Transfer Protocol. It is absolutely necessary that, for a given protocol developed by the Internet Engineering Task Force, the internal identifiers of that protocol be unique. The IETF issues standards known, for historical reasons, as Request for Comment (RFC), as well as managing the drafts from which these standards develop.
Another, much lower-volume role of IANA is to ensure uniqueness of internal protocol identifiers. When the Internet was U.S. government funded, IANA and the RFC Editor functions were carried out by the same group of people. When a working group of the IETF on a protocol, it would describe its identifiers to IANA, who would maintain the IETF master reference lists of assignments. In the RFC Editor function of preparing RFCs for publication, still at the Internet Society, one of the final checks was that all protocol-specific identifiers were consistent with the master lists, and the identifiers were unique across the set of documents that might use them.
Domain Name Service
Much more controversial, and driven by markets, political and ideological bodies, and bodies dealing with intellectual property such as trademarks is the top-level policy-setting and administration of the Domain Name Service, which is an ICANN responsibility.
Just as detailed address assignment is delegated to Regional Internet Registries, detailed naming administration is delegated to registries for the highest hierarchical part of a domain name, such as the .org part of www.citizendium.org. Registries manage top-level domains (TLD) such as .com, .net, and .edu, as well as TLDs based on International Organization for Standardization (ISO) country codes, such as .ar for Argentina, .ca for Canada, .cn for China, .de for Germany, .jp for Japan, .ru for Russia, .uk for the United Kingdom, .us for the United States of America, .tr for Turkey and .zm for Zambia.